M43photo has published an interesting article that compares the auto-focus speed between the Panasonic GH2 and the GH3. Panasonic has already claimed that the GH3 is the fastest auto-focusing camera in the world so naturally, the GH3 should win against the GH2, right? In reality, the answer appears to be a bit more complex than this. The reviewer used the Sigma 30mm f2.8, and Panasonic 12-35mm f2.8 X lens.
Check this article out.